Every day, several quintillion bytes of data may be created around the world. This data comes from everywhere: posts to social media sites, digital pictures and videos, purchase transaction records, bank transactions, sensors used to gather data and intelligence, like climate information, cell phone GPS signal, and many others. This type of data and its vast accumulation is often referred to as “big data.” This vast amount of data eventually is stored and maintained in storage nodes, such as solid-state storage drives (SSDs), and the like, and these may reside on networks or on storage accessible via the Internet. This stored data may require processing, or be subject to operations, such as search, query, encryption/decryption, compression, decompression, and/or other processes. In a server platform, for example, a processing device, such as a central processing unit (CPU), performs operations on the data. The data may be read from the SSD, processed by the CPU, and the processed data may be sent to the source of a request. However, a host or server operates based on logical addresses of the data, and is not aware of the physical location (e.g., also referred to as NAND flash physical addresses) of the data on the SSD.
A flash translation layer (FTL) provides the mapping from the host logical address to flash physical address. It is desired for this mapping to be unaffected by and remain consistent across power cycles. A typical FTL maintains this mapping information in a linear mapping table, which may be referred to as a logical-to-physical (LtoP) map table. The LtoP table has one entry per logical block, with each logic block representing the smallest contiguous piece of logical block address (LBA) that is addressed individually by the LtoP table. Size of the LtoP table is linearly proportional with SSD size, and, for example, may be several gigabytes for a large SSD (e.g., an SSD that is several terabytes in size). It is desired for an FTL algorithm to be capable of rebuilding the translation table in a short amount of time during system power on. The power on time is system dependent but is typically in order of few seconds (such as 2 to 4 seconds). If the FTL algorithm is not able to rebuild the translation table in that amount of time, the host may not be able to detect the SSD during the boot-up process.
Current solutions have various shortcomings. One current solution is to write the entire LtoP table to non-volatile memory (e.g., flash memory) upon power fail and read it back at power on. While this may be a simple answer to the problem, it requires incorporating an array of capacitor banks (e.g. super capacitor banks) in the system. However, super capacitor banks add additional cost and complexity to the SSD and the charge capacity of the super capacitors degrades over time, which may lead to reliability issues and recovery failures.
Thus, there is a need for a system and method for a more efficient flash translation layer operating in the SSD, particularly during a drive power cycle.